The left is abuzz about an error in the 2010 paper by Carmen Reinhart and Kenneth Rogoff showing that when debt reaches 90 percent of GDP or more it has a negative effect on growth. Expect to hear a lot more about this, as if the entire notion that there might be some limits to how much it's advisable for a government to borrow rests on this one paper.
Update: Here, as predicted, is Paul Krugman.